xfs: don't reset i_delayed_blks in xfs_iread

i_delayed_blks is set to 0 in xfs_inode_alloc and can't have anything
assigned to it until the inode is visible to the VFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>